1. Field of the Invention
The present invention relates to an image display device and an image display method for displaying a selected video on a screen thereof by switching between a television program video screen and a graphic user interface video screen, between a television video signal and a computer video signal, or between a television program video screen and a screen for inputting character. The present invention also relates to a television receiver and an image display method for receiving a plurality of broadcast types and displaying a program video of the received broadcast type.
2. Description of the Related Art
Television receivers typically display a television program guide and a variety of setting menus in a graphic user interface (GUI) in addition to ordinary television programs.
For example, Japanese Laid-Open Patent Publication No. 2001-103388 and Japanese Laid-Open Patent Publication No. 2001-186436 disclose digital television receivers. The television receivers acquire television program information from digital data transmitted from a broadcasting station, produce an electronic program guide (EPG) by analyzing the program information, and display the EPG on a display screen thereof via an on screen display (OSD) circuit. The television receivers thus can assist users in the selection of a television program.
Japanese Laid-Open Patent Publication No. 2002-359789 discloses another digital television receiver. The television receiver acquires program information from a television signal decoded by a decoding circuit, produces graphic data of a program information screen by analyzing the program information, and displays the program information screen in an OSD fashion by overlaying a television signal that has been subjected to predetermined image processing. Users thus can acquire, for example, various descriptions of a program prior to or in the middle of a view operation.
Further, Japanese Laid-Open Patent Publication No. 2003-143433 discloses a digital television receiver that displays a variety of setting menus of television and an electronic program guide as a GUI screen.
Japanese Laid-Open Patent Publications Nos. H8-111822, H8-30247, and 2003-44024 disclose television receivers that are connected to a personal computer (PC) and can display a computer video in addition to ordinary television videos. Japanese Laid-Open Patent Publication No. H10-42205 discloses a television receiver that, with the Internet connected thereto via communication means such as a modem, can display a computer video screen (Internet browser screen) in addition to ordinary television video screens.
Japanese Laid-Open Patent Publications Nos. 11-306117 and 2002-199244 disclose television receivers that, with the Internet connected thereto via communication means such as a modem, can display a computer video, such as an Internet browser screen and an electronic mail browser screen, in addition to ordinary television video.
Japanese Laid-Open Patent Publication No. H11-308544 discloses another television receiver. The television receiver displays, on a screen thereof, a software keyboard containing alphabet characters and Japanese kana syllabary to input characters on an Internet browser screen and an electronic mail browser screen. With a remote controller operated, the television receiver receives desired characters and symbols.
FIG. 1 illustrates a schematic structure of a conventional television receiver. The television receiver includes a tuner 1 for selecting a desired channel from a television broadcast wave received by an antenna, a television signal processor 2 for separating a received television signal (composite signal) selected by the tuner 1 into YC separate signals (a luminance signal Y and color signals C) and converting the signals into the primary color signals R, G, and B to output, and an Internet processor 3, having a so-called dial-up connection function, for connecting the television receiver to the Internet via a server of a provider through a communication line.
The television receiver further includes a remote controller photosensitive portion 4 for receiving a command signal input on a remote controller (not shown) by a user, and a microcomputer 5 for detecting and analyzing the command signal received by the remote controller photosensitive portion 4, and issuing predetermined control signals to the tuner 1, the television signal processor 2, etc. In response to the operational command from the user, the microcomputer 5 controls the Internet processor 3 to connect the television receiver to the Internet, acquires content data via a desired uniform resource locator (URL), converts the content data into the RGB video signal, and exchanges data of electronic mails.
The television receiver further includes a switching and synthesizing portion 6 for selectively switching between an RGB signal (television video signal) obtained by the television signal processor 2 and an RGB signal output from the microcomputer 5, or synthesizing the RGB signal from the television signal processor 2 and the RGB signal from the microcomputer 5 for output. The switching and synthesizing portion 6 is controlled for switching and synthesizing by the microcomputer 5.
If an “Internet” function is selected on the remote controller by the user, the microcomputer 5 controls the Internet processor 3 to connect the television receiver to the Internet for interactive communications. The microcomputer 5 also controls the switching and synthesizing portion 6 to display an Internet browser screen of FIG. 2.
Similarly, if an “electronic mail” function is selected on the remote controller by the user, the microcomputer 5 controls the switching and synthesizing portion 6 to display an electronic mail browser screen of FIG. 3. At the same time, the microcomputer 5 controls the Internet processor 3 to connect the television receiver to the Internet to exchange electronic mails.
If the user called a “software keyboard” by operating the remote controller in order to enter characters on one of the Internet browser screen and the electronic mail browser screen, the microcomputer 5 outputs a predetermined video signal from an internal memory (not shown) and controls the switching and synthesizing portion 6 to display the software keyboard screen of FIG. 4. The user can input characters easily by operating the remote controller while viewing the software keyboard screen displayed on a display (not shown). Alternatively, without using the software keyboard, the user may enter characters on one of the Internet browser screen and the electronic mail browser screen directly using any of other input means.
Generally, when a browser software program is initiated on the television receiver having the above-referenced Internet connection function, a browser screen is displayed while ordinary television programs are not displayed. When the above-mentioned software keyboard screen is displayed, ordinary television programs are not displayed.
As technology advances in recent years, conventional analog broadcasting is being replaced with digital broadcasting. In Japan, digital broadcasting started with CS broadcasting by communication satellites in 1996, broadcasting satellite (BS) broadcasting digitized in 2000, and terrestrial broadcasting digitized 2004. Digital broadcasting includes a plurality of broadcast types, such as television broadcasting, radio broadcasting, and data broadcasting. By operating a broadcast type switch on a remote controller, for example, the user can select a desired broadcast type, thereby viewing a broadcast program content.
For example, the radio broadcast type includes radio broadcasting for broadcasting a video and data linked thereto, and radio broadcasting for broadcasting audio only. Depending on program, a sound having a compact disk (CD) grade quality can be enjoyed. Data broadcast type includes independent data broadcasting for broadcasting data only, and linked-data broadcasting for broadcasting data linked to one of a digital broadcast television program and a digital broadcast radio program. When a linked-data broadcast program is received, a user may operate a linked-data display key arranged on the remote controller to receive one of a television program and a radio program currently received and display on a screen.
Corresponding to the diversification of broadcast type mentioned above, Japanese Laid-Open Patent Publication No. 2001-275051 discloses a digital broadcast receiver that displays received digital broadcast information and an operational status of the receiver in an easy-to-understand manner. FIGS. 5A and 5B illustrate the disclosed digital broadcast receiver. The digital broadcast receiver includes a received information display 100 arranged on the front center of the body of the receiver. The received information display 100, as a backlight-type liquid crystal display device, detects a resolution and a format of a video signal, and identification information of broadcast type identifying television broadcast type, radio broadcast type, or data broadcast type. In the received information display 100, a microprocessor acquires these pieces of information from a receiving portion and a decoder, and variable controls the emission color of a backlight source. In this way, the user can check the broadcast type currently being received or on air by viewing the emission color of the received information display 100.
On the other hand, liquid crystal display device displaying broadcast video program by employing an LCD panel as passive-type light modulating means are widely used instead of cathode-ray tubes (CRTs) as a television receiver in recent years. The liquid crystal display device includes a pair of transparent substrates having electrodes thereon and a liquid crystal interposed therebetween. By controlling a voltage applied on each of drive electrodes arranged in a matrix, the liquid crystal display controls a group of or an orientation of liquid crystal molecules to change transmittance of an illumination light from a backlight source arranged behind the transparent substrate. The liquid crystal display device thus displays an image on the LCD panel.
A monitor of a personal computer (PC) for displaying a computer video typically works at a screen luminance level of around 250 cd/m2. In contrast, a television receiver for displaying a television video, typically a natural image (live image), needs a luminance level of 450 to 500 cd/m2. In particular, efforts are made to achieve high luminance in the television receiver employing a liquid crystal display, for example, by improving backlight.
The luminance level (luminance intensity) of the backlight source is determined to within a manually-operated adjustment range of a user. Regardless of the type of the input video signal to be displayed, the luminance level remains constant. Thus, if a graphic user interface (GUI) video, which is rather closer to a computer video such as an electronic program guide and a variety of setting menus, is displayed on the television receiver with a high luminance level set for television video displaying, the screen luminance becomes too high and the screen becomes too bright. A long time of viewing such a screen leads to eye fatigue of the user.
A major portion of power consumption of a large liquid crystal display device is attributed to a backlight unit thereof. Also in respect of reduction of environmental burdens, reducing power consumed by the backlight unit is needed.
It is contemplated that the level of a luminance signal to be input to a display panel is controlled through video signal processing of a luminance signal adjusting circuit in response to mode switching between a mode of displaying a television video and a mode of displaying a computer video. With this arrangement, an image may be displayed at a screen luminance comfortable to the user but no power saving effect is expected.
If one of the Internet browser screen, the electronic mail browser screen, and the software keyboard screen, each being a still image requiring character entry and closer to a computer video, is displayed on the television receiver set at a high luminance level for television video displaying, the screen becomes too bright due to much higher screen luminance. A long time of viewing such a screen leads to eye fatigue of the user.
The digital broadcast receiver, disclosed in Japanese Laid-Open Patent Publication No. 2001-275051, changes the color of the backlight of the received information presentation portion providing information relating to reception, such as a receiving channel, in response to the broadcast type currently received. However, the digital broadcast receiver doesn't take into consideration the screen luminance of a video display displaying received video data so that the user eye fatigue and power consumption are not reduced.